Coherent Phase Line Enhancement (CPLE) is a technique for analyzing spectral characteristics of high speed rotating turbine machinery. The CPLE technique is employed because of its benefits for detecting synchronous and harmonic phenomena. For example, for the main engines of the Space Shuttle, accelerometers are used to sense vibration within pumps and turbines. Frequency analysis through fast Fourier transforms of the accelerometer data are used to detect, predict, and avoid potentially catastrophic engine failures. For example, vibrations within rotating machinery, occurring at first, second, third, or some other Nth harmonic of the rotational frequency can alone, or in combination, indicate current operating conditions within the machinery. These indications can further indicate the degradation of internal components, such as a bearing failure, which if left uncorrected, will result in further degradation or failure of the machinery. Therefore, when using CPLE, it is highly desirable to have to the accelerometer output sampled synchronously at a frequency which is proportional to the rotational speed of the rotating shaft, engine, pump, turbine or similar rotating machinery component.
Using techniques available in the art today, the sampling time of the accelerometer signal is estimated and the physically sampled data is interpolated back to desired synchronous sampling points to obtain a synchronous data set. Unfortunately, both the estimated synchronous sampling times and the data interpolation introduce errors into the analysis. In addition to producing errors, estimation of the sampling times and data interpolation functions also increase onboard data processing requirements. Further, problems with estimating shaft rotation and calculating interpolated accelerometer samples are exacerbated when the machinery is starting up and when the machinery is slowing down because the rotational speed of the machine is changing. For high speed rotating turbine machinery, start-up and slow-down are critical periods of operation for detecting, predicting, and avoiding failures. For performing an analysis such as CPLE, it is highly desirable to eliminate these sources of errors and the associated processing requirements.
For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the specification, there is a need in the art for systems and methods for synchronizing digital sampling having reduced error levels compared to existing techniques.